I have had the 104.2 and they are definitely vastly different, the uni-q gives a different type of presentation of the mid range. I would say I prefer the tweeter on the 104.2, the 105.3 lacks the sparkle.
105.2 all original, just finished a proper maintenance service for them. Had a spare set of oem kef 105.3 3 way binding posts I installed on them.
105.3 are rebuilt with original drivers. I have a Kube 200 for them but not using it at this time.
I am driving them with a Yamaha a-s2100, cd-s2100, and VPI Scoutmaster Prime.
Both complete with all grills. Crossovers original and crossover caps test fine all original
Impressions
I can't really say if one is better, they have wildly different voicing. Major differences noted that yhe 105.3 extract more detail and have a much more expansive sound stage, and present height detail more clearly. Much more dynamic and forward. Much better for complex recording. Theu can be overwhelming at times. You really feel like you're almost swimming in the mix. Bass response is much better running a massive ss amp with the Kube on the lf section only.
The 105.2 have a bit more of a holographic image, overall a bit more 'musical' . Stinged instruments and vocals have a more natural timbre, a live sound. It is eery how well presented the image is, never heard anything like it. I definitely prefer their bass response, not as articulate or fast but it digs deeper a bit more naturally and seems more full and natural.
I have had the opportunity to demo the current line of kef reference 3 as well as the kef ls50 meta at home, have in store demod the reference 5s... and I have to say the voicing is almost identical to the 105.3. I mean if it was first impressions a/b comparison you wouldn't know the difference. The modern iterations are a little less fatiguing, and have a little lf bump par for the course of modern speakers. The 105.3 have more meat on the bone in the mid range, but you have to be in to that sort of thing I guess .But it is marginal. It's shocking how similar the sound is on their modern line to these 30 year old behemoths. Almost like they're just repackaging an old design(though they are more efficient and look nicer